David Styles

Lecturer in Life Cycle Assessment · Bangor University · company speakers →

Expanded boundary life cycle assessment was applied to quantify environmental effects across plausible biogas scenarios for large- and average-sized UK dairy farms. Under default settings, biogas derived from slurry-only systems led to global warming potential (GWP) and abiotic resource depletion reductions of 14% and 67% for the large dairy farm, but eutrophication and acidification burden increases of 9% and 10%, respectively. Co-digestion of grass and maize did not further reduce net GHG emissions owing to additional concentrate feed required to maintain milk production. Marginal GWP changes per tonne of dry matter feedstock ranged from +93 kg CO2e for maize to -1971 kg CO2e for food waste. Conversion of an average-sized dairy farm to a beef-plus-biogas farm led to a GWP reduction of 30% assuming milk production shifted to an intensive dairy farm, but this reversed to a 13% GWP increase when possible iLUC associated with marginal concentrate feed production was accounted for.

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